# If an emitter current is changed by 4 mA,

Question:

If an emitter current is changed by $4 \mathrm{~mA}$, the collector current changes by $3.5 \mathrm{~mA}$.

The value of $\beta$

1. 7

2. $0.875$

3. $0.5$

4. $3.5$

Correct Option: 1

Solution:

(1)

Given :

$\Delta \mathrm{I}_{\mathrm{E}}=4 \mathrm{~mA}$

$\Delta \mathrm{I}_{\mathrm{C}}=3.5 \mathrm{~mA}$

we know that, $\alpha=\frac{\Delta \mathrm{I}_{\mathrm{c}}}{\Delta \mathrm{I}_{\mathrm{E}}}$

$\Rightarrow \alpha=\frac{3.5}{4}=\frac{7}{8}$

Also, $\beta=\frac{\alpha}{1-\alpha}$, so

$\beta=\frac{\frac{7}{8}}{1-\frac{7}{8}}=\frac{7}{1}$

$\beta=7$

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